Firing mechanisms for firearms should meet a number of criteria. The firing mechanisms should be relatively lightweight so as not to add unnecessary weight to the gun, and yet must also be sturdy and dependable. Moreover, the number of component parts in the firing mechanism should be minimized, and these parts preferably should be easily formed without requiring undue amounts of machining, so as to keep down the overall cost of manufacturing and assemblying the firearm.
Still another criterion, particularly with so-called "automatic" or autoloading semiautomatic-firing firearms which fire a single round each time the trigger is pulled, is a firing mechanism which cannot easily be converted to full-automatic firing. A particular case in point involves the "Ingram" pistol, a version of which is disclosed in U.S. Pat. No. 3,651,736. The firearm as disclosed in that patent is designed and intended for full-automatic firing, that is, the pistol automatically reloads and fires while the trigger is pulled, until all rounds in the magazine are fired. Although a semiautomatic-fire version of this pistol has been produced, it is nonetheless desirable to provide an improved semiautomatic firing mechanism which fits within the basic frame envelope of the pistol with minimum modifications, which yields dependable hammer-fired operation with an economy and simplicity of firing mechanism components, and which is not readily convertible to full-automatic firing without substantially rebuilding the gun.